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The parents of around a dozen babies in the trial – who are unborn or in intensive care – now face a nervous wait.

The 93 parents who received sildenafil in a trial to try to stimulate their baby’s growth, were told that it may have increased the chances of potentially fatal lung disease.

The trial, which began in January 2015 in 10 Dutch hospitals, was intended to treat women whose babies had life-threatening growth issues.

It was hoped the drug would increase the size of the placenta and encourage their development. Another 90 pregnant women were given a placebo.

But 17 babies in the sildenafil group were diagnosed with lung disease shortly after birth, and 11 of these died.

In the control group, three babies had the same lung disease but none of them died, according to reports.

In total, 19 babies who were born prematurely in the drug group died, compared to nine in the control group.

“The chance of lung disease appears to be greater, and also the chance of death following the birth seems to be increased,” said a letter sent to the parents involved, according to Dutch television programme Hart van Nederland.

Suzanne de Lange and her husband Martijn, whose baby died after they took part in the trial, said the news had thrown them into turmoil.

“We had made peace with the fact that our daughter Olivia died eight days after she was born,” Suzanne told local broadcaster NOS.

The trial involved pregnant women being given a generic form of Viagra to attempt to boost their babies' growthCredit:
Alamy Stock Photo

“The cause was natural, we thought. And we had come to terms with it. Until on Friday evening we were called by the UMC hospital in Leiden and told it might have had something to do with the study we had taken part in.”

Wessel Ganzevoort, chief researcher and based at the AMC teaching hospital in Amsterdam, told Hart van Nederland that they were focusing on supporting the parents.

“I have spoken to a number of these patients and they are of course very emotional about this, as I am too,” he said. “They knew…that it was uncertain, but now they have to live with the thought that they took part in something that caused potential damage. That is incredibly sad.”

He told the NOS broadcaster that 10 to 15 women who took part in the trial do not know what the outcome will be for their baby: some are still pregnant, and a number of parents have babies in intensive care.

But he said that earlier, small-scale studies into using the drug in this way, had shown positive results.

“The medicine was being used in practice, but we felt it was too early to just introduce it,” Ganzevoort told the NOS. “We wanted to do a thorough investigation first.”

Trials in the UK, Australia and New Zealand in 2012 had found no benefit from the drug, but also no side effects.

A spokesperson from the AMC was unavailable to speak to The Daily Telegraph.